text:
Where can I get blueprints of older aircraft?
I'm currently working on a project for an internship that involves modifying a 1959 Cessna 150. I won't actually be modifying a Cessna 150, but it's more of a "if you did modify it here's how you would, what would happen, and what it would look like." I'm trying to convert it to hydrogen power. I found a suitable new motor and "replaced" the engine, along with removing the fuel tanks. I know I still have a bit more to remove, but I need a place to store the hydrogen and some other stuff. I could put it in the wings, but because hydrogen takes up a whole lot more room than the original fuel, I would likely need to store it somewhere else as well. I need to find empty space that I can store it in. Also, because the new motor is lighter than the original engine, the plane is now aft cg, so I want to avoid putting it in the back. I can't find the blueprints of the original Cessna 150 anywhere, and I don't have a real one to go off of. If possible, where can I find the blueprints/schematics (preferably for free, cause i'm broke)? And if I have to buy them, what's a good place to get them from?

Blueprints and similarly detailed drawings for aircraft are not something that is generally available outside the manufacturer of the aircraft.
For a time, aircraft delivered to the US military were required to include full blueprints for every part.  I do not know if this is still the case.
I have been involved with a few WWII aircraft restoration projects.  We obtained complete sets of drawings on microfilm from the Smithsonian institution.  I do not know how we obtained them -- but there were dozens of rolls of film each with hundreds of drawings for each aircraft.
Even if you only had to pay for the cost to duplicate the microfilm, it would surely cost more than you are willing to spend and would likely take longer than the scope of your school project.
I suggest you talk with your professor about how they think you should progress.  What level of assumptions and details do they expect you to make?

For your purposes a simple cutaway like the following ones should be enough (source first cutaway and source second cutaway):

If you need a bigger version you can ask the editor or the owner of those cutaways.
As you can see, in the tailboom behind the firewall there's still a lot of usable space as well as behind the pilot and copilot seats. Obviously putting weight there is going to shift your cg but this is something that you are for sure already taking into account


text:
How Long Will Boeing Keep the 737 in Production?
Due to the immense costs involved in the certification of a new type, Boeing has continued to iterate upon the initial 737 type with the most recent models being the 737 NG and MAX.
Will they continue upgrading and remaking this type well into the future, or will they move to a new type for their next narrow body design?
Another potential factor is how significant the damage done to the 737's reputation is in the aftermath of the MAX incidents and accidents, and how this may impact future decisions.

Im not sure (without input from someone high up at Boeing) this question can be answered factually. Unfortunately opinion based questions are off topic here.

It seems that "input from someone high up at Boeing" is going to be hard to come by, seeing as the "high ups at Boeing" have packed up and left.

I think it is a good question. Opinions can be based on facts/data.

@Gabe Let's hope that opinions are always based on facts and data, even if the facts are "chocolate pleases me more than vanilla".

The closest answer you will be able to find outside of internal sources at Boeing, is
As long as airlines keep buying them
Kind of obvious, but as long as there is a demand for the 737, Boeing will continue production. According to Wikipedia they had around 6200 737s on backorder in 2023, so this is not likely to happen anytime soon.
Considering that the only other viable option in most of the world for a similar sized aircraft comes from Airbus, Boeing is unlikely to end production without a replacement. Even if they announce a new model to replace the 737, there is likely to be an overlap for a while to deliver all the ordered airplanes not converted to the new model and to cover airlines not willing to add a new model to their fleet.
As long as the 737 can remain competitive
This is also kind of obvious, and is related to the above. Once an airliner is noncompetitive, the only remaining customers are likely to be various military forces. If this happens it is likely to end with the same as the above, with a new and more competitive model being introduced to remain a viable option to the Airbus A320.

Boeing has made it very clear in several earnings calls with their investors that they will not develop a new airliner anytime soon. At the moment, the industry seems to be in a kind of holding pattern as all big manufacturers wait for propfans like the CFM RISE to become ready for large-scale deployment.
Meanwhile, both Boeing and Airbus are experimenting with very high aspect ratio wings, Boeing with the transsonic truss-braced wing on the Boeing / NASA X-66 and due to an accidentally leaked rendering, we can speculate that Airbus is working on a very high aspect ratio gull wing design.
It seems like both of the big manufacturers are trying to hold out on designing a new airliner until they get very high aspect ratio wings, propfans, active wings, new materials, and hybrids / hydrogen / SAFs figured out. There are so many new technologies "right around the corner" right now that designing a new airliner too early would mean you miss out on some breakthrough.
That means for the foreseeable future, it is likely that all we are going to see is modest upgrades to the B737, B787, A320, and A350.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Which Piston General Aviation Aircraft Engine Has the Longest TBO?
After doing some initial research, it appears most GA piston engines have a recommended Time Between Overhaul of around 2,000 hours. I was wondering if there are any other engines that may have a significantly longer TBO. Do modern diesels developed from car engines such as the Austro E4 have longer TBOS due to their contemporary design, or are manufacturers hesitant to sign off on longer periods of operation?

A brief googling says the Austro E4 AE300's TBO is 1800 hours.  Maybe the newer designs aren't newer in terms of metallurgy, lubrication, wear, fatigue and whatnot.

@CamilleGoudeseune They are newer, but the effort is going towards better power/weight ratio and better fuel efficiency, since these play more role in initial purchase decisions.

For a private owner (part 91), TBO is not a legal requirement. It is a guideline. Anecdotal, I have heard from partnerships which fly on for 6,000 hours. If you know your engine, and you have a good mechanic, and do regular inspection to catch things, then you may get away with much longer intervals. It depends on the complexity of the engine, whether it is regularly inspected, whether various systems that do degrade such as pumps are replaced, and whether you have realtime diagnostics in the plane to catch problems. There are certain engines that are problematic, such as turbo charged, or geared engines. If it is your plane, you know your engine, you know the sound, or any vibration, and you also need a good mechanic, who  can figure out compression, oil consumptions and other metrics to determine engine health.

Noting that TBO isn't binding for Part 91 doesn't really answer which engine has the longest published TBO.

@Ralph J: No, but it does hint that the correct answer to OP's title question is "The one in sbrunner's plane."

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Why would there be a drag discrepency when simulating transonic flow over scaled CRM geometry?
I have a discrepancy when simulating a wind tunnel experiment of a 2.7% scaled NASA CRM geometry as used in the wind tunnel.
I am trying to replicate exactly the wind tunnel model and flow conditions of the AMES Wind tunnel experiment of NASA CRM by setting the right mach number, static temp and pressures to match the measured tunnel values. At the moment, all the fluid properties match perfectly as described in the AMES experimental data.(density, Re etc)
Coming to the geometry, I have modeled the AMES tunnel wall boundaries and the scaled CRM geometries at the different angles of attack as tested in the papers. Wall boundaries are given the appropriate boundary conditions.
It is a static rigid model, not flexible.
A well refined mesh with a y+ of 40 was created and simulated in these conditions
Turbulence model chosen was SST K-omega, with all the methods set to 2nd order. (ANSYS Fluent)
3 Key observations were noticed:

Shock position was slightly ahead (~5-10% x/c) compared to experiment
Cp peak values were 10% over predicted
Drag Coeff prediction was ~30% underpredicted compared to experiment (Lift Coeff was extremely good ~ <1%)

I have 2 theories for the discrepancy in drag:

Unresolved boundary layer and hence effect of viscous drag is not being modeled
Wind tunnel model is not rigid, and its aeroelastic bend twist coupling is causing delay of separation due to shock, but I don't get how drag would be higher in that case

What would be a logical next step in determining a good agreement with the experiment?

Any changes to the solver or flow properties I am missing?

*Also as a query, would it make sense to try running a sim of the full scaled model, in the transonic flow regime, with the same Re and flow conditions in cruise as well? I am not sure how it will be a good method to validate my wind tunnel setup. Would the maintenance of Re and Mach number be enough to make the transonic cruise case and scaled wind tunnel experiment comparable?
** In case you are wondering which papers I am trying to replicate, it is the validation of the transonic wind tunnel model of the CRM by NASA.

By CRM you mean the Common Research Model? The half-model of an airliner without tail? At what angles of attack? Sorry, but this question is far too unspecific and only allows speculation. If you want meaningful answers, please provide meaningful information.

First, have you done a grid resolution study?  Not just the boundary layer, but everything?  Shoot for a halving and doubling of your mesh (i.e. one coarse and one fine) and then try to apply Richardson extrapolation.
What wind tunnel corrections have been applied to the experimental data?  Are you comparing to the raw or corrected data?
Exactly what wall boundary condition did you apply?  Transonic wind tunnels typically have perforated or slotted walls that do not behave like a solid wall (viscous or inviscid).
How is the model supported?  Did you model the sting?
No aircraft or wind tunnel model is truly rigid.  They may have attempted to correct for some flexibility already, but that remains an area to question.
Many of the CRM models have been used as AIAA DPW cases.  Those studies typically have summary papers where many sets of results are compared and discrepancies are investigated.  You should find the most similar cases and study those.

Sorry, upvotes are limited to 1 per person. This answer deserves many more.


text:
Could a WW2-era Grumman Hellcat land on a Saipan-class light carrier using only reverse-thrust generated by a reverse-pitch propeller?
Just that - take away an F6F's arrestor hook and fit it with a reverse-pitch-capable propeller (and, of course, all the other odds-and-ends to make such a system work).
Would it be possible for a decently trained and experienced naval aviator to land such a modified Hellcat on a 186.2m long (611 ft) flight deck with anything approaching safety and repeatability?

It wouldn't be a "WW2-era" Hellcat any longer with that sort of prop on it.  Beta range works well, with immediate reverse thrust, because the prop stays at 100% RPM and the pitch goes negative quickly. Could the original engine spin a prop that way? Maaaybeee.... but it wasn't designed to do that, so now it's not just a new prop, but more mods. Hard to know what the sum of such hypothetical modifications would or wouldn't be able to do.

Thanks for the answer. From what I understand, NACA and BuAer was already testing reverse pitch props on a Curtiss F6C-4 all the way back in the early 30s as a possible method of dive braking - so we're not exactly talking space-age technology here.


text:
Any sites that track/report primary radar?
Most (all?) web sites that display real-time tracking display ADS-B or Mode-S transponder data. But if an aircraft is not broadcasting, then only a 'skin paint' will be visible. I know that FAA radars return both transponder data AND raw radar RF energy returns.
Is anyone aware of any web sites or any public APIs that have access to Primary radar data from FAA radars to track  targets that are not squawking?

In the US at least, FR24 does use FAA radar data: https://www.flightradar24.com/how-it-works#faa

@jacron, can you help me navigate the FR24 site to replay historical data from 22 Apr?  So far I've been unable to figure out how to do that.

I’m on my mobile right now where I believe it’s not supported but check https://support.fr24.com/support/solutions/articles/3000120423-how-to-view-playback-on-the-flightradar24-website-

Thanks.   Will do that.


text:
How to identify a flight without any information
On 22 Apr, at 10Am, I watched a small, fixed-wing, single-engine turboprop aircraft orbit over my neighborhood for about 2 hours. I estimate its altitude at about 5,000 ft.  It flew near-perfect circles, arriving at exactly the same point overhead exactly every 300 seconds.  The location, less than 10 miles from IAD, is clearly within rhe Consolidated Potomac TRACON. None of the real-time tracking sites (FlightAware, ...) showed any aircraft flying that pattern, so I concluded that it was either not squawking ADS-B or Mode S, or that the web sites were requested to not track the flight.
I've seen this same behavior several times over the past few years with the orbit centered over different nearby areas.
How can I find out what this flight was doing or who it was?

Have you called the TRACON and asked them?

Yes. I called.  TRACON said they "could not divulge that information."  Considering the area being observed and the aircraft, I doubt it was a local police operation- they usually use rotorcraft anyway.  More likely a DHS training operation or some local tech company testing a new sensor of some sort.  Still, it would be interesting to know what it was all about.

As discussed ADSBx is helpful, but in controlled airspace they are usually talking to tower or approach. “Idaho” is one call sign they use.

Your options are fairly limited. If you think it was broadcasting ADS-B or Mode S, you can check on one of the sites that does not respect requests to not publish ADS-B data, like ADS-B Exchange. You could even set up your own ADS-B receiver if you want to make sure your area has good coverage in the future.
Failing that, you could do an exhaustive search through LiveATC recordings to try to identify communications they made. If you believe it may be police or similar you may also be able to find recordings people made of local police scanners and other public communications.
The most sure way is the most low tech. Next time the aircraft passes by, go read its tail number with a spotting scope or a good pair of binoculars!

Thanks @chris, next time (?) I'll give ADS-B Exchange a look.  At the altitude the aircraft was flying, I'd need a tripod-stabilized scope and a better angle than I've managed in the past.

@Chucko ADS-B Exchange lets you replay older data so you could give it a try now. Though I didn't see anything around KIAD flying a pattern like you described at a quick glance.

I looked in real time, while the airplane was visible directly overhead.   There was no ADS-B track displayed on any of several tracking sites.  So I'm not surprised that historic replays showed nothing.  Either the ADS-B track was being ignored by the tracking sites or, more likely, it was not squawking, alwas operating VFR and being tracked by TRACON as a primary radar target.

@Chucko Doesn't have to be a primary target. A mode 3/A transponder will not show up on tracking websites either. I mentioned ADS-B Exchange only because they very specifically refuse to ignore any data available to then. Granted they still might not have the data if there was no volunteer with a receiver in range.

Reading the number with binoculars might be difficult, using a digital camera might be easier. Take several still photos and some video zoomed in on the plane, then when back home you can view the images on a computer monitor and zoom in on the registration number and hopefully make it out. A smart phone camera might be good enough, a digital camera with optical zoom probably even better. As for binoculars, see if your pair has a tripod screw hole on the front. If it does you can buy an inexpensive attachment that lets you mount the binoculars onto a tripod.


text:
How do tubojets compare to afterburning turbofans in terms of efficiency?
Turbojets used to be more common in the 40's and 50's but once jet engine design matured they pretty much went extinct in favor of the more efficient turbofan. I know one advantage of the turbojets is the high exhaust velocity which allowed a lot of turbojet aircraft at the time to supercruise, turbofans typically need the assistance of an afterburner in able to reach similar speeds at the cost of a lot of fuel. It's very common to see faster fighter/interceptor type aircraft to use low bypass afterburning turbofans (for the purpose of this question, lets say about 1.5-2.0). This is for obvious reasons, the vast majority of an aircraft's lifetime is spent at subsonic speeds so the turbofan makes a lot more sense, and the afterburner is there for the rare occasion it's gotta go like a bat outta hell.
My question is, say you have two hypothetical aircraft, both identical with the exception of the engine, one with a turbojet (no afterburner) and one with an afterburning turbofan (like I said, bypass ratio is somewhere in the ballpark of 1.5-2.0), both aircraft weigh the same, have the same coefficient of drag, and have the exact same top speed, (something greater than Mach 1). So both jets have similar high speed performance, which jet should we expect to be more fuel efficient, the turbojet at max thrust, or the turbo fan with afterburner on, at max thrust?

How do tubojets compare to afterburning turbofans in terms of efficiency?

The 5th slide from this presentation (original plot from Daniel P. Raymer, Aircraft Design: A Conceptual Approach), shows a qualitative comparison of the specific fuel consumption of several propulsion technologies:

As visible, until around Mach 1.6 the fuel consumption of a typical low bypass turbofan is better than a turbojet. Afterwards the pure turbojet becomes more efficient and the turbofan just gives up at around Mach 2, mainly due to aerodynamic limitations of the fan.

I don't think there were "a lot" of turbojet aircraft that could supercruise.  There were some (at least the F-106), but that doesn't constitute a lot.  Please provide an authoritative list of more -- or a quote for this being more common.
The aircraft of that day had to be very clean (aerodynamically) because they did not have enough thrust otherwise.  Consequently, most of the Century Series fighters carried their weapons internally.  The B-58 mostly fits into this category, with a special conformal weapon, but using afterburning turbojets.
I suspect that the F-106's supercruise was under very specific conditions -- without weapons.  Not in combat ready configuration.  All of these aircraft still had afterburners.
The next generation of fighters (F-4, F-5 etc.) still used turbojets.  They moved back to externally carried stores.
The other important case here is the Concorde -- obviously designed for efficiency (as much as a supersonic aircraft can be).  It could supercruise on turbojets, but also had afterburners.
The F-14, 15, 16, 18, etc. all use afterburning turbofans.  They are much more efficient than the preceeding turbojets.  I also expect that they are superior in terms of engine specific thrust (thrust to engine weight ratio).  Engine technology improved substantially throughout this time.  They of course carry their stores externally.
5th gen aircraft go back to carrying their stores internally, but now for stealth reasons -- but they get an aerodynamic benefit.  The F-22 and F-35 still have afterburners, but of course the F-22 can supercruise.
This is all to say -- there is a lot going on between these generations that mean you can't really make the comparison you're suggesting.
In order for the two engines to have equal thrust -- the non-afterburning one would have to be much larger than the one with afterburner.
An afterburner lets you add a tremendous amount of thrust -- with terrible TSFC (fuel consumption) for very little added engine weight -- it is a long hollow tube.
To get the same thrust without an afterburner, you would need to increase the diameter and length of an engine.  It would have better TSFC, but would be larger, heavier, and more expensive.
We consider how much time you need to spend at maximum speed and consider that against the rest of the mission requirements.  It does not seem that turbojets win out anymore.
Edit: Add a bunch of hopefully relevant performance data.
Here are some performance figures for the aircraft in question.  Hopefully this is a fun addition to the conversation.
F-104.  At this gross weight and load out, it does not appear to have any super cruise ability.

F-106.  At this gross weight, it can barely supercruise at a narrow window of altitudes.

F-4.  Unable to supercruise, but this shows the dramatic difference a change in load out can make -- the numbered bubbles are for different missions

F-15.  Slight supercruise ability.  This figure is nice because it shows Ps across the envelope -- both dry and wet.  Notice the Ps 'island' at Mach 1.9 and 36,000 ft.
There is a thrust pinch transonically -- where drag rises much faster than thrust.  This makes Ps very bad transonically, but can lead to an operating window that is better supersonically.  This is why some aircraft would climb high subsonically and then dive through the transonic area to get to supersonic flight.  This is actually the optimal time to climb procedure for some aircraft.  Similarly, when aircraft do supercruise, they sometimes use AB to get through the thrust pinch and then oeprate on the other side.

XB-70  Some supercruise, but unsurprisingly it really was designed to go all out.

If you look at the Wikipedia article on Supercruise, you won't see any of these aircraft listed.  Instead, all the aircraft that appear in that list are super cruising at a much higher Mach number.

Okay my ignorance is showing, I guess I assumed that super cruising turbojets were much more common then they actually were. I'm seeing the flaws in my question and you pretty much answered it. There's a ton of nuance to cross-generational comparisons like this and if I'm not mistaken, super cruising Isn't a whole lot easier for turbojets and the majority of supersonic turbojets relied on afterburners which kind of defeats the point of my original question.

"I suspect that the F-106's supercruise was under very specific conditions -- without weapons." If you meant internal vs external, F-106 weapons were all internal. 4x AIM-4 and 1x AIR-2A Genie.

@WPNSGuy Agreed -- I was more thinking about flight at lower gross weight.  I recall a coast to coast F-106 flight (possibly near retirement of the type) that was impressively fast.

And the Six still apparently holds the FAI single engine speed record (In a very unloaded condition, and a few engine mods). https://www.f-106deltadart.com/speedrecord.htm


text:
Can you identify this plane?
Can you identify this plane?

Unknown airplane
I have just found the photo on a CD together with many other planes and helicopters. I have no clue regarding the place where the picture was taken, the time and the type of the plane.

Google reverse image search seems to think it's a IAR 80, but someone who knows more than I would need to confirm.

Roddy, I had no idea Google has such a feature. This is amazing. I have tried, in the meantime, with another 2 planes and Google found them immediately. Thank you very much.

IAR 81C according to this page: The IAR-81 fighter-bomber (same tail number).

Thank you for introducing me to a very interesting plane :)

@mins, that indeed appears to be a cleaner scan of the same photograph.

@Roddy is correct. It is an Romanian IAR-80 all right.

"IAR80" by user:Planck -  licensing policy.. Licensed under Public Domain via Commons.
IAR-80 was produced by IAR (Intreprinderea Aeronautică Română), an airplane manufacturer that was the property of the Romanian State until the end of the WWII. The aircraft first flew in 1938 and was in service till 1952.
The model appears to be the IAR 81. The same image can be found here. It was probably taken in the eastern front.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Who invented the canard wing?
Who invented the canard wing?
I know that early planes like those built by Santos Dumont and the Voisin brothers used canard wings but who invented the canard wing?
Update
The plane built by Hiram Maxim and tested in 1894 had a canard wing for pitch control.

(source)

(source)
Hiram Maxim's plane
So, it is quite evident that this type of wing was not invented by the Wright brothers as some people believe.

https://en.wikipedia.org/wiki/Canard_(aeronautics)#Etymology

Related (and it likely answers the question): What is a canard?

Read all about it here

Short answer? The Wright Brothers. The term was coined to describe the Santos-Dumont 14-bis, as its design with a box-like array of forward control surfaces looked like a duck in flight, but the very first successful powered aircraft was a similar canard biplane with a pusher engine.
As planes developed after the Wrights' first flight, this design fell out of favor for a number of reasons. To save weight, the horizontal and vertical stabilizers were grouped together so a single set of braces could support them, and when this arrangement was forward of the wings in the most logical pusher configurations of the day, the planes had a general tendency to nose away from the relative wind, which caused issues with takeoff and landing as well as unrecoverable deep stalls as the plane kept its nose high or even swapped ends in a stall.
These behaviors led to the concept that's familiar to us today, of a central barrel fuselage with the engine and prop in front, the pilot behind that and an "empennage" of horizontal and vertical surfaces in the rear. This arrangement allows for better stability and easier recovery from stalls by having the empennage point the nose into the relative wind, much like a weathervane. The downwash of air over the horizontal stabilizers also allowed that stabilizer to have a reduced pitch angle, reducing drag. These and other advantages led to the arrangement becoming dominant in aircraft design as of WWI (with a couple notable derivations in the early war, like the D.H.2 "pusher" which allowed a machine gun to be mounted along the pilot's line of sight before the invention of the synchronization gear) and continued into the second and third generations of the jet era.
The return to a "pusher"-style powerplant with the modern turbojet led to a revisit of the idea of a forward horizontal control surface. The design has a few advantages, especially in combination with a delta wing which became common on the second-generation supersonic jet fighters. Canards provide a lift force in the direction the pilot wishes the nose to go, instead of opposite that direction, so when pulling up, the canard adds to total lift. Canards also allow the primary pitch surfaces to encounter relatively undisturbed air, as opposed to a tail-mounted stabilizer, which increases the effectiveness of the surface. The larger rearward delta wing acts as the "empennage" of a traditional plane would, helping keep its nose in the wind, and the vertical stabilizer remains at the rear of the plane, avoiding the shortcomings of early canard designs.
Several experimental designs were tried as early as the war years, but the Saab Model 37 "Viggen" was the first aircraft of the modern era to use a canard-delta planform configuration, in 1967. This design has since become a favorite of European designers, with the Gripen, Typhoon and Rafale all following this basic configuration. The Russians have incorporated canards into a few of their fighters like the Su-30 to augment a traditional all-moving tail elevator, and the PAK FA has a similar concept with movable "leading edge root extensions". American designers have played with it, in programs like the F-15 ACTIVE tech demonstrator and the XB-70 prototype hypersonic bomber, but the sole production U.S. aircraft to use canards does so mainly for stability; the B-1B Lancer has a small pair of canards linked to the FBW system which dampens oscillations in the forward fuselage.

Actually, the fist Canard was the Wright glider of 1900. The Wrights initially never considered an aft tail because they felt putting the small surface in front would avoid the stall condition which killed Otto Lilienthal.

I edited; first successful powered aircraft.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
How is a confusion possible between Western and Russian Attitude Indicators?
Yesterday I watched a documentary on Crossair Flight 498 accident. One of the factors that might have contributed to the accident was the confusion of the pilot on interpreting the attitude indicator; he was initially trained with Russian model (right) instead of Western model (left):

But looking at both type of indicators, could anybody tell how the confusion is possible? In both models, if you see the indicators turning your head right (as if you were sat on the plane's seat), both show that the right wing is "touching" ground. That means that you are clearly rolling right. How can a pilot interpret that the plane is rolling left?

I find that a weird graphic.  The gauge is relative to the pilot so it always appears 'square' from their frame.  Rotating that gauge, in my opinion, make it harder to understand what the pilot might have misunderstood.

@RomaH, I agree. This image is not representative. I have attached more suitable one in my answer.

This confusion is also suggested to play a part in Tarom flight 371's crash

It's so easy to sit in our comfy lounge chairs and wonder how on Earth pilots get things wrong.
The error didn't happen without context. It was dark. There was little to no external visual reference due to cloud. The pilots were manually flying in a busy phase of flight. And the captain was probably adversely influenced by a medication/opioid.
Even without the artificial horizon mixup, the conditions were ripe for spatial disorientation.

This image is taken from this short video (yellow arrows were added). It demonstrates how a left turn on the Soviet display is similar to a right turn in a Western display.
The captain was used to the left display, where if the main line of focus was angled to the left, that would mean he needs to make a right control input to go back to wings level. In the accident flight, he saw that the most predominant line - the horizon on the Western display - was angled to the left. Due to the context I've mentioned, he went back to his basic knowledge - that a left angle means I need to make a right control input.
Of course, if he was on top of his game, he would have remembered that even on the Soviet indicator, the artificial horizon should have been level. But by this point he was already disoriented and confused, with the first officer's instructions ambiguous and worsening his dilemma.

It's so easy to sit in our comfy lounge chairs and wonder how on Earth pilots get things wrong. That was rude, because in my message I did not say anything that put pilots's professionality in doubt. Actually I have a deep respect towards them, not only because of their work but also because I'm getting my pilot license (ultralight aircraft). Anyway, your answer was useful to understand the reason. Indeed the prominent lines in both types of indicators might lead to confusion. Thank you.

@Claudix sorry you feel that way, I wasn’t attacking you personally. There is just a tendency for many people to dissect pilot actions in an accident and throw accusations without realising that in the right circumstances, everyone can make a fatal mistake.

"...wonder how on Earth pilots get things wrong."  That's easy.  They don't get it wrong on Earth.  They get it wrong in the air :)

Western planes should have had a sphere/trackball to turn the "rest of the world" instead of a yoke/sidestick to turn the plane. :)

The basic premise has been mentioned by everyone above: the basic instinct is to 'right the wrong', and if we see some indication tilted left, we instinctively want to move it right. It's possible to train for everything, but in stressful or confusing situations instincts will take over, it's just a question when.
The reverse ('Russian') indication didn't appear just out of the sense of opposition to the West; it was a product of extensive research. It's been proven that pilots make less mistakes with the reverse indication, from lab tests to the statistics of successful spiral dive recoveries.
Conversely, the direct ('Western') indication is more the result of gradual evolution: early AH had a gyro right in the central ball (or directly connected to it) that represents the horizon, and it naturally kept the 'true' horizon line. (Except that sky and ground were reversed, with the blue or white half at the bottom). And after all, it's just 'obvious' that Artificial Horizon should show, well, horizon!
But there is one more dimension to it. The mental picture of motion is different for different people. Some (apparently, about half or even the majority of) people perceive it better as them being at the origin and the world moving around them. This corresponds to the direct ('Western') indication, and such people must adapt to it more naturally. They also tend to use maps with 'track up' orientation.
Others view (or can easily imagine) themselves from the third person view, and they are more at home with the reverse (and 'north up') display. There was a research (I'd need to find a reference, but it will probably be in Russian) that fighter pilots with this second type of mind perform better in a dogfight.
That said, in a really stressful situation all the complicated mental pictures disintegrate, and the most basic instincts remain...

Just adding few more points to the already existing answers. I agree with previous commenters - some understanding of pilot perception and context is needed.
@Claudix, the image used in your original question can be misleading for 2 reasons:

Both instruments are tilted to the right side on your original image. This is, however, not how pilots would see the Attitude Indicator (the instrument itself). Even if the aircraft banks, pilots do not tilt their heads. In fact, in smooth coordinated turn without outside visual clues, you won't notice that your aircraft is actually banking to the side. Your body will sense that you are perfectly level, because at the same time the lift component has been also increased.

On a real Western digital Attitude Indicator (display), that little aircraft silhouette in the middle might not be very distinct, as depicted on your original image. It can be also obstructed by Flight Director bars. As Ben pointed out, the most predominant line you might see is the horizon line. The horizon line is what's moving on a Western instrument, and this is what might confuse pilot. In contrast, on the Russian instrument, the aircraft silhouette is moving in front of a static horizon.

To better illustrate your question, I'm attaching this image to show 2 different ways of displaying an aircraft during banking. The upper instrument is the Western display, the bottom one is the "Russian". Both instruments are showing roughly 30 degrees banking to the left, but in two completely different ways.

I'm not a professional pilot on a large glass cockpit aircraft, but I have PPL with some Instrument flight time logged, and find that the "Russian" attitude indicator might be more intuitive and easy to read in some situations.
As an example, if pilot must perform sudden and unexpected upset recovery, to correct the attitude, he might be misled by a very predominant diagonal horizon line on the Western display.
The problem is - it's the horizon line which changed its position in relation to the Western AI display. Consequently, a pilot under stress and / or "tunnel vision" might want to return the horizon line back to it's original position by turning the yoke in the wrong direction, with potentially catastrophic consequences.

Thank you, I finally understood the reason behind the confusion. Regarding to your point #1, I know the indicators are depicted in a weird way. This is why WE (not the pilots in their cockpits) have to see the image with our heads tilted. Anyway, my image is clearly misleading. Thank you!

I think the biggest factor is that under intense stress where the "mental tunnel vision" effect starts to take hold (I've had that experience in the simulator) you revert more and more to your most base line and strongest mental foundations (and if they aren't there you simply freeze).  So, while it may seem easy-peasy to adapt to, until the western format has been internalized as deeply as the Russian one, there can be a tendency to start to mentally revert, causing more mental conflict and accelerating the mental tunnel vision effect, ending up in mental freeze mode.

I was taught in and flew single and twin Pipers, Beechcraft and Cesnas in the 1980's. All these aircraft had the Russian style FAI, although we referred to them as ground pointers. I'm now flying modern glass cockpits using Western (skypointer) FAI. Although I understand the logic in the Western instrument is better, personally I prefer the Russian style. 10,000 hours later and I still sometimes get tripped up.

Thanks for sharing this experience, but how come that these (Western) aircraft had 'Russian' FAI?

This answer will tackle the question from the perspective of "How might a pilot trained on the Western style of attitude indicator be confused by the Russian style of attitude indicator?"  This should also shed some light on the reverse question.
In both of the instruments shown in the question, there is no doubt that brown is showing above the left wingtip of the airplane icon, meaning that the airplane is banked left.
Yet confusion could arise when a pilot used to seeing the Western style artificial horizon, where the moving thing is the horizon not the airplane, assumes the moving on the Russian style is also the horizon, not the airplane.
The exact same source of confusion often arises when a pilot who is used to focusing his attention mainly on the (Western style) attitude indicator tries to fly primarily by reference to the "turn coordinator"- where the moving thing is the airplane, not the horizon.  It is very common for relatively inexperienced pilots to react in the "wrong" direction to the turn coordinator, as if the moving thing were the horizon rather than the airplane.  This possibility for confusion is one reason among several why many pilots prefer the traditional "turn rate indicator" (aka "turn and slip indicator") to the "turn coordinator"-- despite the fact that by sensing roll as well as yaw, the "turn coordinator" tends to give a stronger indication than the turn rate indicator when an aircraft first starts to roll into an unwanted turn.
And here's a way to take this potential for confusion an even higher level: see this early-generation piezoelectric turn rate indicator manufactured by the Belite company.  This product (unlike some later products by the same company which really are turn coordinators with a sensing axis canted away from the vertical to pick up roll as well as yaw) is really just a yaw rate indicator and nothing more.  But the way the indicator is meant to be read, is that the illuminated LED lights are meant to depict the wingtips of the aircraft.  In a left turn, the lower left and upper right LED lights would be illuminated.  This can be confusing to a pilot who assumes that the symbolic airplane (which never moves) is meant to illustrate the airplane, while the LED lights are meant to depict the horizon, after the manner of a Western-style attitude indicator rather than a turn coordinator.  To avoid this problem, at least one pilot has found it helpful to completely hide the aircraft symbol behind a picture of a fixed horizon line, with brown earth below and blue sky above, or better yet, to completely hide the airplane symbol behind an abstract symbol designed to suggest that the left and right wingtips of the airplane are moving in an arc with their present position indicated by the LED lights.  This helps make it clear that the symbology employed in the device is actually following the same presentation as is employed in the Russian-style artificial horizon, which is also the same presentation as is employed in a "turn coordinator".  Despite the confusing fixed illustration of the airplane, the moving thing represents the airplane, not the horizon.  Some pilots have felt that a simple arc of LED lights across the top of display representing the movement of the needle of a traditional turn rate indicator, with the airplane symbol completely omitted, would have been a more effective presentation of the information sensed by this instrument.
A comment in closing-- it seems that the Russian style of attitude indicator would be very confusing to interpret at bank angles beyond ninety degrees, where the aircraft is inverted.

Re the last comment: not really. First, the airplane figure was usually distinctively asymmetric. More so than the horizon line anyway. Second, there is rarely a confusion when the airplane is statically inverted; the usual trouble at such attitudes is that the airplane constantly turns and spins and it's unclear which way to recover. This is where the reverse/Russian indication shines most: you just oppose the turning motion of the indicator, even if you can't make out the details.


text:
What airplanes can I fly with an EASA PPL license?
Weird as it might seem, I'm not 100% sure what airplanes I can fly
with an EASA PPL(A) license. During the training the instructors would
tell me that I can fly airplanes up to 2000 kg MTOW and 5 passengers
or so, but I think they are wrong and this applies only to the (old)
national rules (Germany in this case).
The license states that I have a SEP (land) class rating. I have
searched through the EASA rules (a cumbersome task on its own) and
nowhere could I find a weight or passenger limit, nor a specific
definition of what exactly qualifies as a SEP.
So the question is, what aircraft am I entitled to fly with my PPL(A)
license? Do aircraft with specificities such as a retractable
gear fall into the same category? Please also point to the source
of the applicable legislation.
By the same token, may I/may I not fly light aircraft such as e.g. a
K-10 Swift?

It sounds like your instructors (or you?) mixed up the rules for PPL(A) and LAPL(A).

PPL EU-FCL SEP entitles you to fly any aircraft with a single piston engine. No turbines, no jets, but on the other hand... as far as EASA is concerned, no weight or pax restrictions. These come into play for the LAPL.

I was wondering about the same and here is what I found.
Yes, for LAPL license holders, when switching to another airplane within the same class rating (don't mix it up with type rating) the familiarization training shall be performed and signed off by instructor. It's stated in the "FCL.135.A LAPL(A) — Extension of privileges to another class or variant of aeroplane" section of the "Part FCL".

Before the holder of an LAPL can exercise the privileges of the licence on another variant of
aeroplane than the one used for the skill test, the pilot shall undertake differences or familiarisation
training. The differences training shall be entered in the pilot’s logbook or equivalent document and
signed by the instructor.

There is no such requirements for PPL(A) holders.
Further away there is the section "FCL.700 Circumstances in which class or type ratings are required" which has class rating SEP (land) with many aeroplanes: SEP (land), SEP (land) with variable pitch propellers, SEP (land) with retractable undercarriage etc.

All those are aeroplanes. The D to the right means that

Whenever (D) is indicated in one of the lists mentioned in paragraphs (a) to (c), it indicates that differences training in accordance with FCL.710 is required.

Ok, going down to the "FCL.710 Class and type ratings — variants" where we have

In order to extend his/her privileges to another variant of aircraft within one class or type rating, the pilot shall undertake differences or familiarisation training.

I don't know why aircraft is used in this section instead of aeroplane, but later again it's explained as

(a) Differences training requires the acquisition of additional knowledge and training on an appropriate training device or the aircraft.
(b) Familiarisation training requires the acquisition of additional knowledge.

Conclusion: the minimum required is "Familiarisation" which is just "acquisition of additional knowledge" which has no any requirements for legal sign off or so.

You can fly any airplane with PPL even B737 if you own one. Well to fly B737 you will need IR, ATPL exams as it's multi crew airplane, MCC and TR. I don't know if it makes sense but you can put everything on PPL if you want.
You only have SEP so you only can fly SEP airplane. SEP is just any airplane with single piston engine. But CAA can decide to require TR for any aircraft if they consider it to be complex...
If you get IR and TR and you can fly private jets without problem with PPL. But you see that to get everything you will need to know the same theory as for ATPL license.
As for K-10 Swift it's Ultra Light aircraft. Regulations differ by country I think. In my country CAA doesn't issue ultralight licenses but ultralight planes association.  General rule is that you will need difference training.

So the point is there is no weight and passenger limit for SEP per se. However there is implied limit simply because anything above certain weight requires TR as does, if I remember correctly, anything with a turbine and anything above 12 passengers requires multiple engines.

I don't want to look like I come here, ask a question, and then leave without a trace... There is a reason why I cannot accept your answer. Note that you say SEP is any airplane with single piston engine, but then go on to imply that somehow a K-10 Swift does not fall into this category... The question still holds: what requisites does an airplane need, so that it can be flown with an EASA PPL(A)?

K-10 Swift is ultralight and CAA doesn't issue licenses for them. Well SEP is any airplane with single piston engine minus exceptions.

My understanding is that if you are not flying for commercial purposes the PPL has no limits on the aircraft weight or complexity. You must however have a Type Rating for the aircraft beyond Sep if required.
I have flown a few fast jet types on a PPL with a CAP632 which can be issued by any qualified instructor if they are satisfied you have met the military training standards. Hope that helps.

With an EASA PPL(A) you can fly single engine piston aircraft, for example the Cessna 172 or the tiger moth

Welcome. Could you provide references to sustain this answer (links to authoritative documentation)?

Tiger Moth would require  tail wheel endorsement in addition to the SEP that's granted with the EASA PPL.


text:
What was the average duration of a Me-262 combat mission during WWII?

Me 262 in 1945
Maximum speed: 900 km/h
Range: 1,050 km
Service ceiling: 11,450 m
Rate of climb: 20 m/s at max weight of 7,130 kg
Thrust/weight: 0.28
Could a Me-262 fight for (1050 km) / (900 km/h) = 70 minutes?

Range usually means a fuel-efficient cruise speed/altitude. "Fighting" is very much fuel inefficient, so it could not "fight for 70 minutes". Also at it's maximum speed, its range would be greatly reduced (again, range is a fuel-efficient power setting, not max speed).

@RonBeyer: Pilots normally selected full power on takeoff and touched the throttles only for descent and landing. Playing with the throttles like you do on a piston aircraft would be a sure way to risk a flameout. So it pretty much every time flew at maximum speed.

If memory doesn't fail me, I've read that the TBO for those early turbojets was only 25h. The reason was the lack of availability of proper alloys for their construction. Those turbojets were, however, designed in such a way that dismounting and servicing them required no special tools, and could be even performed with the simple means available in a bicycle repair shop.

This depended strongly on the flight altitude. Staying at low level for the full mission meant that the Me-262 would run out of fuel within 40 to 50 minutes.
Climbing above 6 km (20,000 ft) would extend that time to 90 minutes. Time to climb to 9 km was 13.2 minutes, so that would leave a time for engaging the enemy of 60 minutes. Considering that typical armament were 24 unguided rockets and 4 cannons with 80 or 100 rounds means that the 262 would run out of ammo in much less time.
One pilot told me that a typical training mission would start in Munich, continue to a radio station near Berlin and back to Munich, all within 60 minutes.

OK, I was impressed before with all of your answers, but where did you find an Me-262 pilot to chat with about their flying?  I would have loved to have been a fly on the wall for that.

@Marius: That was more than 30 years ago.


text:
How many kilowatts to get an electric 747-8 airborne?
Reading about the Airbus E-Fan and it's dual 30 kW thrust fans caused me to wonder: assuming the need for four electric fans, how many kilowatts would be required to power each fan with enough thrust to get a Boeing 747-8 airborne?

How do I turn this into a community question? I feel completely unqualified to mark any answer as the accepted one since I don't have the electrical and physics background to know if any answer is accurate or best.  I asked the answer hoping to be enlightened but don't consider myself a suitable judge to rate the answers.

The point of allowing users to vote on answers is to show a consensus on what the best answer is. If you don't feel qualified to accept an answer, then you don't have to do so. Changing it to a community question won't change any of that, and will also prevent users that answer from earning any reputation.

Another way to calculate it is to do it from fuel: say we use 747's data: 8mg/n*s of SFC, with take off thrust being 1100kn, with JP-A being 40MJ/kg, and thermal efficiency being aroung 40%, we arrive around 140MW.  If you drive the fan with electric motor, it's subject to the inefficiency of the fan, too. 90MW calculated as below is the output power of the fan, but in practice the shaft power that drives the fan needs to be higher.

Instead of the you can use a small nuclear reactor for powering the turbofan.
That reactor is save as it is pressurized water

First, let's figure out how much power a 747 needs to takeoff:
Assume:

Engine thrust = 284 kN
Takeoff speed = 170 knots
Takeoff power = 90% max power

Using $P=Fv$, converting the variables to SI units, we get
$$Power=88,948,800 W$$
Or, in other words, around $90MW$.
EDIT: This calculation is only correct if the engine efficiency is 100%, because it is based on work done. For a realistic estimation, see Jan Hudec's answer. I'll leave the rest of this answer based on 90MW as I'm too lazy to update the numbers.

But just exactly how much is 90 megawatts?
An average laptop computer consumes 20W on daily use. You can power 4.44 million laptops with this power.
A high-end desktop consumes 300W under heavy load. You can power 300,000 desktop computers. If you stack 20 of them in a server tower and put 100 towers on each floor, you need a data center with 150 floors to fit those machines in.

Let us take this a step further and evaluate the total energy needed for a flight. Assume all required energy comes from onboard energy storage (i.e. no solar panels / windmills). Let's also assume a full power climb to cruise altitude of 15 minutes, 50% power cruise for 4 hours, and a completely idle descent which does not consume any power at all.
Using $E=\int P dt$, we get the total energy needed for a flight is $$720,485,280,000 J$$
With that amount of energy, you can pull a 735 kiloton object up 100m. If all those weights are water, that's close to 300 Olympic swimming pools.
If you power the whole plane with batteries, you'd need 47 million AA batteries.

Of course, if you manage to get 14 of these electrical 747s together, you can generate 1.21 gigawatts and get Back to the Future.

Without the use of superconductivity there is no electric motor technology currently available that would be light enough to be a viable candidate to turn the fan to achieve such power. Jet engines just have extreme power densities

That would be about 720 tons of lithium-ion batteries for the flight (assuming a specific energy of 1 MJ/kg). And likely more because of the peak current required for takeoff. Also 300 m² would need to be available (2.43 MJ/l)

Thanks for putting that 90 MW into perspetive. All this can be seen as an argument againt electric flight but I just see it as an ode to how much energy is stored in a fossil fuel.

I do not see a solution for the batteries, but the current technology for electric motors is not so far off. What is the weight of the 747's engines? 4x4 = 16 tons? Look for HTS (high temperature superconductive) ship propulsion, e.g. http://www.electric-vehiclenews.com/2009/06/navy-tests-worlds-most-powerful.html . This example (120 rpm, 36 MW, 75 tons) is way too heavy, but it is designed for ships, and for the navy. I am convinced that it is possible to design an electric jet from scratch for aviation, and to achieve 16 tons or less for 90 MW nominal power.

@bogl there's no such thing as an "electric jet"...a jet engine is, by definition, non-electric.

@kevin is that so? Have a look at https://en.wikipedia.org/wiki/Arcjet_rocket . But feel free to replace 'jet' in my comment with 'turbine'.

@kevin ... as well as https://en.wikipedia.org/wiki/Jet_propulsion. Any machine that jettes out a stream of matter for the sake of propulsion could be named 'jet engine'.

For comparison, the Eurostar trains are just 12MW: https://en.wikipedia.org/wiki/British_Rail_Class_373

@kevin: Don't confuse the layman's use of the word "jet" with the technical term "jet". Squids and octopuses use jet propulsion. The technical term for jet engines are turbines (unless of course it's a ramjet). You may wonder why we call windmills turbines as well - that's because turbojet engines are basically windmills (only at really high temperatures and pressures).

Another way to put the 90 MW in perspective would be to compare it to nuclear power plant output, which is somewhere in the range of 500 to 1000 MW per reactor (note: reactor, not plant). This means that you need somewhere between 1/5th and 1/10th of a common electrical grid nuclear reactor to power that plane during takeoff, depending on how big a reactor you are willing to bring along.

90 MW? You are from an efficient county! 90 MW won't get a 747-8 anywhere! The problem is that you only count the work done on the plane. That is enough when talking about wheel-driven vehicles, which use huge reaction mass (Earth) that can absorb any amount of momentum with practically zero work. But aircraft don't have that luxury. Their only available reaction mass is the air and that takes a lot of energy with the momentum.

Ok; I've done the estimate (see the answer). It's not 90 MW, it's 200!

@JanHudec is absolutely correct. It makes no sense to use aircraft velocity for computing engine power. At zero aircraft velocity, you still need shaft power to produce thrust.

@JanHudec It's a reasonable estimate.  An aeroderivative Rolls Royce RB211G-DLE, from memory, generates about 30MW of shaft work in stationary applications.  As an aircraft engine this same powerplant puts out about 250kN of thrust.  The 747-8 uses four GE GEnx engines at 300kN, probably at a higher efficiency, but let's say 36MW scaling with thrust.  Four engines makes 144MW, so this answer's estimate is at least reasonably in the ballpark.

@J..., the figure for the derivative turboshaft is continuous power while the question is for the 5-minutes-max TO/GA power. My estimate of 183 MW (4×45.7 MW) below matches 144 MW continuous quite well (yes, this answer is in the ballpark, but we can get more accurate than ballpark).

@JanHudec Indeed, but I suppose when it's a question of putting wings on something this size, a factor of two, give or take, really doesn't make much difference.

I can't quickly find the necessary numbers for 747-8, so I'm going to go with the numbers for Rolls-Royce RB.211-524G-T, one of options on 747-400, taken from here.
The engine can produce static thrust
$$ T_s = 58,000\ \mathrm{lb}_\mathrm{f} = 258\ \mathrm{kN} $$
using mass flow rate of
$$ \dot m = 1,604\ \mathrm{lb/s} = 727.5\ \mathrm{kg/s} $$
Now due to principle of action and reaction, the engine must apply the thrust to the air passing through it. We know that $ F = ma = m\frac{\Delta v}{t} $ and using $ m = \dot m t $ we get $ F = T_s = \dot m \Delta v = \dot m v_e $, where $\Delta v$ is change of velocity of the air inside the engine, which is equal to exhaust velocity $ v_e $, since we are starting with still air. We can solve for exhaust velocity:
$$ v_e = \frac{T_s}{\dot m} \approx 355\ \mathrm{m/s} $$
That's pretty fast. In fact, it is mildly supersonic, though in practice it is average of the just subsonic bypass flow and the faster hot core flow (in which the speed of sound is higher).
We also know that kinetic energy is $ E = \frac12 m v_e^2 $ and, deriving by time, power is $ P = \dot E = \frac12 \dot m v_e^2 $.
So we can substitute:
$$ P = \frac12 \dot m \frac{T_s^2}{\dot m^2} = \frac{T_s^2}{2\dot m} = 45.7\ \mathrm{MW} $$
That's one engine.
Total power is 183 MW.
For 747-400 with this particular type of engines. Different engine options will have slightly different powers, because they use somewhat different mass flow rates for the same thrust. And of course, 747-8 will have a bit more.
The above also used static case. At higher speeds, the pressure recovery allows turbine engines to produce even more power, but by the end of take-off run, the pressure recovery is not significant yet and at altitude, the lower overall pressure limits the output, so this does correspond to the maximum power the engine develops.
With some losses, we are looking at at least 200 MW power input. All the numbers in kevin's answer need to be multiplied by 2-and-a-bit.

I note the  Industrial RB211 is rated at 32 MW.   I infer that this would be down-rated from the aero-engine version to support prolonged continuous operation - so I take this as support for your answer.

@Crosbie, indeed, the 32 MW is most likely the maximum continuous power, while I am estimating the take-off thrust, which is limited to 5 minutes, here. Plus the part of power provided by the hot stream is included here, but not for the industrial version.

The end velocity of 355 m/s would be obtained if the exhaust converts all gas energy into kinetic energy. A convergent exhaust cannot produce supersonic gas streams, and part of the thrust will be delivered as increased static pressure times exhaust area.

@Koyovis: The core exhaust is even faster but still subsonic. Please consider what the speed of sound is in air of 600°C!

@CarlLumma, when deriving the power, the mass $m$ is a function of time, while the velocity is constant. And since the mass flow is constant, it is a linear function of time, so it differentiates to mass flow, with factor 1, and the constant $\frac12 v^2$ remains and there is nothing to cancel the $\frac12$. As a verification, the power being one half more than the shaft version of the engine is plausible, but more than twice is not.

Well, the GEnx-2B67 engines with which the 747-8 is fitted each produce a maximum of $ 284\ \mathrm{kN}$ thrust (according to its Wikipedia page). This translates to a total of $1136\ \mathrm{kN}$, since it has 4 engines.
Power, which has the units Watt, is the product of force (thrust) and velocity.
The 747 has a takeoff speed of about $290\ \mathrm{km/h}$, according to this page.
Assuming the 747 requires all its available thrust for takeoff, the power it requires can be found by multiplying its velocity by the force pushing it forward (in the case of an airplane, its thrust).
First convert these to SI units:
$$1136\ kN = 1136000\ N$$
$$290\ km/h = 80.55\ m/s$$
We now multiply these to get the power:
$$P = 1136000 \cdot 80.55 = 91504800\ W = 91.5\ MW$$
So, for takeoff, the 747-8 will require approximately $91.5\ \mathrm{MW}$ of power.
This is a very crude estimate. Firstly, the maximum thrust listed on the engine's Wikipedia page is likely its maximum static thrust, when it is standing still. When it is moving forward at $290\ \mathrm{km/h}$ at takeoff, this thrust will be slightly less.
Also, if you want to provide this power with electric motors and fans, there are inefficiencies associated with both the electric motors and the fans, which will mean that the actual motors used will in total need to be able to produce quite a bit more than $91.5\ \mathrm{MW}$.
The weight of such motors will be monumental. And these motors will need to be fed by an energy source, batteries or hydrogen fuel cells come to mind, and the weight of these will be just as large.
Electric motors are quite efficient in converting energy, but the energy storage devices that will feed them have very low energy densities (read energy per weight).
Internal combustion engines are quite inefficient in converting energy, but the fossil fuels that they use have an extremely high energy density.

Note that the engines are not always run at maximum rated thrust for a takeoff, so the real-world numbers may be (slightly) more favorable - still the answer is "Probably a lot more Watts than we have space for batteries onboard."

So, um, a lot! Current battery tech is somewhat suitable for moving a car down the road, but not for getting a commercially viable aircraft off the ground.

I doubt batteries would ever be able to power a 747, even just to taxi. The unwritten part of this question is "assuming you had all of the electricity you needed without exceeding the weight requirements of the aircraft..."

I am also quite concerned about the weight of the motors themselves. A 100 MW motor is MASSIVE. As in think next level industrial/mining scale.

There is also the weight of copper needed to shift all those amps around.

This is the sort of situation that makes one think how under-appreciated the extremely high energy densities of  hydrocarbon fuels are. Perhaps because they are so ubiquitous people don't appreciate them as much.

Something that didn't occur to me until reading the answers is that an electrical fan would not only be transferring a forward thrust force to it's mounting pylon, but also a radial torque in the opposite direction as the motors in are spinning the fan itself. Having to deal with the torque forces would require heavier/stronger mounting points, resulting in even more thrust required to lift off and fly.  Even with a small light fusion reactor (for the sake of argument) the weight of the motors and the torque they produce might make this a non-viable idea.

@MikeC. A set of counter rotating props would balance the torque. A failure of one in the set would be disastrous though.

A turbofan engine also generates a torque, I would just think its onset is more gradual as the engine can't speed up as fast as a prop/fan. Thats just speculation I actually have no idea. But physically any rotating machine, be it a turbofan, gas turbine, piston prop, turboprop etc will generate a torque that will need to be constrained.

You are from an efficient county! The value you calculate is the work the engine does on the aircraft. But since aircraft don't have the luxury of huge reaction mass (Earth) that can absorb all the needed momentum with negligible work, there is also the work the engines do on the air. And if you calculate the energy that way (which requires finding a mass flow rate through the engine), you'll get twice as much!

I know this isn't the exact answer to your question, but perhaps this will give you some perspective that other answers haven't.
The Airbust E-Fan electric motors produces 30 kilo-Watts of power.  That is equivalent to about 40 horsepower.  There are two of these, for a total of about 80 horsepower.
The first airplane I soloed in was a Cessna 150.  It was fitted with a 200 cubic inch four cylinder internal combustion engine and could barely carry two people.
Additionally, the Wright Flyer was powered by a four cylinder internal combustion engine that produced 12 horsepower.
As others have shown, the total takeoff power of the 747 is about 90 Megawatts, which is about 120,000 Horsepower.  In other words, you would need about 1,200 of the Cesnna 150 engines, or 3,000 of the Airbus E-Fan motors, or 10,000 of the Wright flyer engines to produce the same amount of power.

how many kilowatts would be required to power each fan

Apart from the calculation of the needed power, this is actually a very nice question to understand why all the fancy electrical-driven aircrafts that the bright future will bring in our skies have a lot of propellers on their wings, the so called "distributed propulsion".
As a first approximation, the power needed by 4 fans/propellers can be calculated, as usual, with the simple momentum theory:
$P=\sqrt{\frac{T^3}{2 \rho A}}$
Where $\rho$ is air density and $A$ disk area $\pi r²$. Each 747-8's GEnx-2B67 engine has a fan with some 2.8m diameter and delivers some 290kN of thrust $T$. Substituting these values in the previous equation gives a total needed power at sea level of:
$P=4\cdot \sqrt{\frac{(290'000)^3}{2 \cdot 1.125 \cdot \pi 1.4^2}}=168MW$

An electrical locomotive needs only some 5MW so that's a lot... but it can be reduced: if we suppose that each propeller can be hung at the same height of the wing (instead of under the wing), then their radius can be doubled anyway respecting ground-clearance. But the total needed power becomes:
$P=4\cdot \sqrt{\frac{(290'000)^3}{2 \cdot 1.125 \cdot \pi 3^2}}=78.3MW$
Much better... but it can be further reduced: from root to tip, the 747's wing is some 30m long. That means that actually five of those propellers could be accommodated on each side of the wing, for a total of ten. Now each propeller must produce ⅒ of the total thrust i.e. $T=\frac{4 \cdot 290'000}{10} = 116'000N$, requiring this time a total power of:
$P=10\cdot \sqrt{\frac{(116'000)^3}{2 \cdot 1.125 \cdot \pi 3^2}}=50MW$
And what if we use contra-rotating propellers? Then we could pack twenty of them on the wing, each producing a thrust of $T=\frac{4 \cdot 290'000}{20} = 58'000N$ for a total needed power of:
$P=20\cdot \sqrt{\frac{(58'000)^3}{2 \cdot 1.125 \cdot \pi 3^2}}=35MW$
And if we duct each contra-rotating propeller? Then a 30% thrust increase can be expected, lowering the total power to:
$P=20\cdot \sqrt{\frac{(0.7 \cdot 58'000)^3}{2 \cdot 1.125 \cdot \pi 3^2}}=20.5MW$
Increasing the number of propellers, the power required can be reduced by a factor 8! Nice! And even nicer is that twenty of these electrical engines might be used, for a total engine weight of $20\cdot 100=2'000kg$ instead of $4 \cdot 6'150=24'600kg$!
So through the use of distributed propulsion, both the needed power and the engines weight can be roughly reduced by a factor 10.

Obviously these are simple quick and dirty calculations which do not take into account any aerodynamic interference among rotors, any structural issue or any practicability of the concept. Anyway, considering that the energy density of lithium-ion batteries is 10 times lower than jet-fuel, the volume being the same and 40 times lower, the weight being the same, one sees that distributed propulsion is the only way to go towards aircraft electrification.

It's completely unfeasable. Without all the calculations (accurate as they may be) a very large Boeing (737 or 747) can't be make airborne with electricity/batteries alone. Maybe hydroelectricity could.
A Tesla mark 3 has about 6200 'laptop batteries'. They weigh about a 1000 kilo's. The electricity regenerated per battery is not that big: about a laptops requirement. The weight would be significant versus the weight of the plane, or the weight of the plane plus the weight of the kerosine.
For making it available for a very large jet (!) fueled engine, enormous techical achievements have to be made.
Can an elictrical powered engine be converted in a jet fueled one? Not with current technology, I think.
John

Can you provide some sources for your claims please?

A single 777 engine develops 108 megawatts of power, with 2 engines, that is 216 megawatts...you are going to need more than 90 megawatts taking off in a 747 if you want to live.

Welcome to aviation.SE. We are looking for factual answers. Would you hapen to have a source for your statements?

Also please note that the question asks about a 747-8, not a 777.


text:
Lost radio communication after take-off in IMC - what are my options?
This might be "yet another lost comms questions", but I've tried to read a lot and there are different answers everywhere. Here's the scenario:
(The flight plan as filed is - KSSI SSI V441 MONIA GNV OCF V581 DADES KTPA)
I'm taking off from an uncontrolled airport - KSSI to fly to KTPA (ICAO IDs). The current weather at KSSI is 003 OVC and 2 SM. I call MACON FSS for my clearance on 121.5, and here's what I get -
MACON FSS: "ATC clears N123CW to KTPA Direct SSI and then as filed, climb and maintain 4000 expect 8000 two-zero minutes after departure, departure control will be 126.75, squawk 1234. Released for departure, clearance void if not off by 20:45, time now 20:30, frequency change to advisory approved."
After read back, I take off exactly at 20:35 and after a couple minutes I contact Jax Center on 126.75 as I'm crossing 1300ft. I hear no other traffic on the frequency, and I try to contact them 2 more times while I'm heading direct to the SSI VOR. I try to contact MACON FSS with whom I'd just spoken a few minutes ago - and I hear nothing back. I try a couple of other frequencies that I can get from charts - no luck anywhere. I'm in complete IMC.
Now, I know that I've lost my radio communications capabilities and hence squawk 7600, and figure out my route and altitude to fly.
I was cleared direct to the SSI VOR, and then as filed. Looking at "AVEF", ATC expects me to fly the route I filed. Looks good - no problems here.
I was asked to climb and maintain 4000ft, and expect 8000ft 20mins after departure.
Looking at "MEA", ATC expects me to be at 8000ft since it's the highest amongst the Minimum En-route Altitude, the expected altitude (which is n/a) and the assigned altitude).
I'm still at 2400ft, climbing to 4000ft.
My questions are:
1) When should I start my climb to 8000ft? Should I level off at 4000ft and wait until 20:55 (which is 20 minutes after my departure time) before initiating my climb, or does ATC expect me to be at 8000ft by 20:55?
2) Along my route (not immediately after departure, but after a while), for e.g. at the GNV VOR, if I briefly enter VMC, should I go ahead and land at the nearest airport as practicable or should I still continue through my route? I do know that the regulations advise to land as practicable when you're in VMC, but if the airspace ahead is being cleared for you when you're under IFR, is it advised to try and land into VFR traffic who have no idea that you're coming-in out of nowhere?
Appreciate all the answers. Thank you!
PS - Here's the Low-Enroute chart for quick reference:

The answers to these questions can be found in the AIM in section 6-4-1. All quotes are from that page.
To the first question, you should expect to receive a clearance to 8,000 feet twenty minutes after departure; therefore, don't climb above 4,000 until that time. If you are still in radio contact after 20:55, the "expect" portion of the clearance expires:

If the pilot received an “expect further clearance” containing a higher altitude to expect at a specified time or fix, maintain the highest of the following altitudes until that time/fix:
(1)   the last assigned altitude; or
(2)  the minimum altitude/flight level for IFR operations.
Upon reaching the time/fix specified, the pilot should commence climbing to the altitude advised to expect. If the radio failure occurs after the time/fix specified, the altitude to be expected is not applicable and the pilot should maintain an altitude consistent with 1 or 2 above.

For the second question, the answer comes down to the definition of "briefly". Is your hole big enough for you to get under the clouds, and is the ceiling high enough that you can remain VMC to land? If so, you should do so. But if you just briefly see the ground, or aren't confident that you could safely fly VFR to a suitable airport, then you should maintain IFR and continue flying your clearance. You may inconvenience a few controllers, but if you leave your cleared route only to discover that your intended airport is socked in, getting back to your route to resume your original destination puts you potentially low to the ground, and not along the route that ATC is expecting you:

Pilots should recognize that operation under these conditions may unnecessarily as well as adversely affect other users of the airspace,
since ATC may be required to reroute or delay other users in order to
protect the failure aircraft. However, it is not intended that the requirement to “land as soon as practicable” be construed to mean “as soon as possible.” Pilots retain the prerogative of exercising their best judgment and are not required to land at an unauthorized airport, at an airport unsuitable for the type of aircraft flown, or to land only minutes short of their intended destination.

That said, VFR traffic should always be looking for other aircraft - with and without radio contact. Radios are not required equipment, at least at non-towered airports, so landing among VFR traffic without a radio should not be a big deal.

What, no squawk 7600 anywhere in your answer?

@MichaelKjörling Procedures like squawking 7600 are mentioned in the question. This answer is strictly about what route and altitude to fly.

The reference to “small private jets” and altitude is invalid.  Our C550B has a ceiling of FL450, and the B737-800 I used to fly had a ceiling of only FL410. Most “small” jets fly higher than “large” jets. Many times due to limitations, and most of the time due to climb performance and or speed envelopes based on weight.
As for making a cell phone call from the plane... fly first, then comm.  Sure, try it, but digital cell towers are directional in the vertical plane and are sketchy above a few thousand feet. Also, cell tower hand-off is hard to rectify when above a few thousand feet. Analog would be the way to do it, but you’d better be operating to FAR compliance first. Remember, ATC isn’t waiting for your attempted cell call.
I’m assuming this OP aircraft only had a single comm radio?  Not ideal.  Even a handheld makes a good backup. I’ve lost COMMS several times over the last 30 years. Some were single point failures, some were electrical failures... only one required light gun signals at the destination.
Know your clearance ‘limit’ and ‘expect’ status. How many note OFF time? How do you know your expect clearance time without it? Guess? Not ideal.
In the case of the OP, the limit is direct SSI and 4000.  The expect is AF and 8000 in 20. With lost COMMS, expect trumps limit after the time expires. Then fly as AF, arrive at approach FIX on time, fly the approach. Look at the tower for the green.  If VMC en route is encountered, squawk 1200 and that will cancel your IFR. But, think about that clearly before you make that commitment. 152 cloud clearance until you can land.
With newer multifunction GPS/NAV/COM units, you drop a lot of gear with a single point failure. Have a backup for both COM and NAV.

Also, at some point, check to make sure you didn't accidentally hit the radio's on/off switch.

"The limit is SSI... the expect is as filed." I don't believe that is accurate. The clearance limit is Tampa Airport—just like FSS said, "cleared to the Tampa Airport via direct SSI, then as filed." Now the assigned altitude is 4000 and the "expect" is 8000, that is correct.

Cell phone, Call the tower, that's what the controllers want. Might not work with a jet, but most GA should be low enough. Always try to have the towers number.
Your over complicating things.

I suspect you'd be hard pressed to use a cell phone reliably at much of the altitude where IFR flight is common. (And if you're really in a pinch, there's no reason why you couldn't slow a jet down to make a call, so the distinction between "jet" and "most GA", which I take that you're using to refer to piston aircraft, isn't the relevant one.) Cell phone base stations are designed to direct the signal along and toward the ground, not into the air. If able then using a cell phone to contact ATC is a possibility, but it sure isn't one I'd count on having available above a few thousand feet AGL.

the Op was talking 4-8k, for terrain clearance even a small privet Jet would plan higher than that, and since cell towers are usually put on the tallest mountains around, actual vertical distance to the cell tower would be much less. have seen 3 bars + at around 5k + agl.

@wanna-beCanadianPilot However, cell phones signal is not omnidirectional and you may not maintain good signal throughout the journey. In Europe, your better luck would probably be 112 as that gets signal from any station, no matter which GSM provider you run under.


text:
Class B and C Airpsace Ring Data in Text
Class B and Class C airspace has multiple rings where each ring can be a custom polygon shape.

I want to extract following data into text:

the shape of these polygon rings in lat/long (ideally a geoJson object)
distance between the rings and
high / low limit for each ring

Is this data available for free or purchase?

FAA NFDC should be the place (for the US).

You might also try asking at GIS.SE.

@mins thanks. this is exactly what I was looking for.

@mins you should turn your comment into an answer.

For the US, the FAA National Flight Data Center (NFDC) is the place. There is this set of files: Class B,C,D,E Airspace Shape Files, which is free and contains borders of airspaces in the GIS shapefile format.


text:
Angle of bank affects on descent rate
I’m attempting to do some maths regarding the ‘impossible turn’ (engine failure after takeoff, followed by a 180+ deg turn back to the field to land). I understand how to determine radius, rate of turn, and best glide descent rate; however, I’m unable to determine how descent rate is impacted in a turn at best glide. My only theory is that the equation for load factor might hold some clue as to the percentage increase in VSI. Is there anyway to determine the loss in magnitude of the vertical component in the turn back to the field and the associated increase in VSI (assuming an engine out best glide profile)? Is there a rule of thumb? Is there an equation? Thank you

Yes, of course.  It's the square root of 1 over cosine bank angle × airspeed.
That will determine speed increase required to glide while banked, but ...
Turn radius favors lower airspeed.  You want to bank but not increase pitch beyond that which maintains proper airspeed for that bank angle.  With no power, the aircraft will start a spiral descent.
Try these at altitude.  Starting with a 30 degree bank.  See which combination of airspeed and bank brings you around with the least loss of altitude.
VSI is not as important as bank angle and airspeed indicator.  That's what you need to be focusing on.
But, please, beware.  Stalling attempting the "impossible" turn at low altitude may not be survivable.  Controlled flight wings level gives one the best chance of survival.
Also, turning from a head wind back into a tailwind (assuming the turn is attempted on take-off) means the ground speed increases 2x the windspeed.  If a sudden tail wind gust does not stall you, the ground speed on landing can be higher.
VSI can be calculated by rate of (180 degree turn) divided by altitude loss as a statistic.  Once this is determined from flight data, it could serve as a reference while a turn is in progress.

Thank you for your comment Robert. But, I believe you have provided the equation for increase in stall speed for a level flight turn. My goal is to find the altitude loss, mathematically, in a turn. And then, given the tool of determining rate of turn, determine VSI. The key I think - is determining the resultant loss of vertical component with an AoB. I don’t think my theory of load factor is correct - If you use the extreme of 89 degs AoB as an example

@RyanBW I would start with Vbg and glide angle at Vbg, which is arc tan glide ratio.  In a bank, Vbg increases by square root of 1/cos theta.  What one must do is calculate (for gliding) is not only the increase in speed, but also the increase in angle of descent (in a spiral) based on the increase in drag, which is compensated by the increase in vertical gravity component.  But, the real key to successfully handing a low level engine out is to immediately initiate the turn at Vbg and best bank angle.  Practice makes perfect.

Alright, I think I get it. I don't think I get this performance though; can you provide additional information regarding the increase in drag? I ask because I get the following - Cessna152 glide performance (1.5 NM per 1,000'), results in an angle of 6.26 deg. 45 deg angle of bank results in an increase of 41% - 8.83 degs. Assuming TAS of 60 knots, radius of turn is 320', and 180 deg turn is 1,000'. Flattening out this half circle, turn back to the field, you lose 155' in 10 secs (VSI 930'/Min). Does this make sense? When I'm practicing the steep spiral, I lose about 700' / turn. Thanks again!

700 feet/turn is pretty close to what I got in a 172, which is 350 feet per half turn.  Work with IAS, remember at 45 degrees stall speed rises from 50 to 60 knots.  Add in more altitude for additional maneuvering as a pure 180 does not align with the departing runway.  I wouldn't do a 45 any slower than 70.  It'll be close between a 30  at 63 knots and a 45 at 70 knots.  You can also try various flap settings.


text:
Why does an APU fitted with a load compressor consume less fuel while operating two packs instead of one (e.g 737NG)?
As far as I know, an APU that takes its bleed air from the compressor section consumes more fuel the more bleed air is extracted, like the engines. Some APUs have a load compressor for the bleed air fitted on the shaft that always spins, and on some aircraft like on the 737NG the APU consumes less fuel with both packs operating on the ground than if supplying one pack only although it needs less bleed air even if the single pack runs automatically on high setting (hence why such a great amount of unused air is then exhausted through a surge control valve (SCV)) Now I still don’t understand the reason for this phenomenon after reading multiple discussions regarding this question. Please correct me if something of the content above is wrong.

@mins  It's an accurate statement. Not sure that the explanation here sheds much light on things beyond what the OP has already read, but what's being discussed is real.

Single pack operation certainly doesn't achieve the same cooling as two packs; other than a single pack regulating to high flow in the AUTO position (which happens with engine bleeds, not APU bleed), I'm not sure how it goes about trying to do so. The way it was explained to me, matching your thought, was that the APU is optimized for the flow & pressure required to feed two packs, and feeding just one is far enough from that optimal point that it actually takes slightly more fuel. But the engineering "why" causing that, i.e. the OP's question, is beyond my knowledge.

I don't think it's related to electrical load. The screenshots of the CDU in the 737.org.uk link I posted above are accurate. You can sit on the ground with the APU running & watch the fuel flow change by turning packs on & off, with no other changes going on.

@RalphJ: Yes, in the meantime I read another information about the additional fuel consumption: +15% for single pack (source, page 28). From what I read the higher fuel flow could be required to supply the same air flow at a higher pressure (this would explain the "work harder" found everywhere on the web), to allow a single PACK to process it alone. Without an authoritative source I won't write an answer.


text:
How is a constant speed of the Engine driven hydraulic pumps maintained (or isn’t it)?
As the N2 rotation speed varies, the accessory gearbox speed also varies and some components like the generators need the constant speed drive (CSD) to maintain the needed speed (unless variable frequency generators are used). How does it exactly work for the hydraulic pumps that are installed on the gearbox ?

Hydraulic pumps are driven directly
Their rotation speed is a direct function of the engine rotation speed. Hydraulic pumps therefore incorporate a solution to maintain a constant system pressure under the dynamically varying engine rotation speed and hydraulic fluid demand. The solution depends on the type of pump.
Spur Gear pump
During most phases of operation, this pump tries to supply the system with more fluid than it needs. A relief valve returns the excess fluid to the reservoir, thus maintaining system pressure.
Axial Piston pump
Here, the swash plate angle is varied to maintain the system pressure. The swash plate angle is controlled by a spring loaded actuator known as the servo piston, which is supplied directly by the pump itself. If the system pressure starts rising (the engine accelerates or the fluid demand reduces), the servo piston forces the swash plate to a finer angle, thereby reducing the pressure. Conversely, if the system pressure falls, the spring forces the swash plate to a coarser angle, thereby recovering the pressure.  Thus, a constant system pressure is maintained.

Thank you very much for the information!

There are also pressurized accumulators for evening out pressure when demand or RPM fluctuates.


text:
What determines which of the two hyd. systems (A and B) available for the primary flight controls is used in manual flight ? (B737)
With CMD A engaged, sys A will be used and with CMD B engaged, then it will be system B. But what exactly determines the hydraulic source used during manual flight (pressure available, system load…)?

During manual flight with hydraulic pressure available, is your question?

That is not the way it works. The two systems operate all the major controls independently so that either system can be used to safely control the aircraft. As you mentioned, the autopilot A for example controls the aircraft by operating on hydraulic system A, and autopilot B operates on hydraulic system B. Unless one system has failed, the pilots manual controls operate on both systems simultaneously.

So this means that both are always used together when flying manually, do you have a reliable source to read more about this operation and the PCU’s operation in general ? Thank you for your information !

@dnblkj - If you google "737 FCOM" you will find the flight crew operations manual is available from many sources.

I think you are confusing the hydraulic power control units (PCUs) which move the control surfaces with the hydraulic servos for the autopilot.
The 737 uses conventional flight controls with steel cables connecting the yokes and rudder pedals to the hydraulic PCUs, which use hydraulic pressure to move the actual flight control surface. Both systems A and B are used for this:

The primary flight control system uses conventional control wheel, column and
pedals linked mechanically to hydraulic power control units which command the
primary flight control surfaces; ailerons, elevators and rudder. The flight controls
are powered by redundant hydraulic sources; system A and system B. Either
hydraulic system can operate all primary flight controls.

(Boeing 737 NG FCOMv2 - 9.20.1 Flight Controls - System Description)
The autopilot also uses hydraulic pressure to operate its servos. But these are not directly connected to the control surfaces. Instead, the servos operate on the steel cables connecting the yokes and the PCUs. This also results in movement of the yokes as the autopilot inputs commands.

The AFDS is a dual system consisting of two individual flight control computers
(FCCs) and a single mode control panel.
The two FCCs are identified as A and B. For A/P operation, they send control
commands to their respective pitch and roll hydraulic servos, which operate the
flight controls through two separate hydraulic systems.

(Boeing 737 NG FCOMv2 - 4.20.1 Automatic Flight - System Description)
As you can see in the following picture and table, autopilot A uses hydraulic system A for its servos and B uses B. But the actual control surfaces are using both hydraulic systems:

Hydraulic Power Distribution Schematic

A and B Hydraulic Systems
Components powered by hydraulic systems A and B are:

System A
System B

ailerons
ailerons

rudder
rudder

elevator and elevator feel
elevator and elevator feel

flight spoilers (two on each wing)
flight spoilers (two on each wing)

ground spoilers
leading edge flaps and slats

alternate brakes
normal brakes

No. 1 thrust reverser
No. 2 thrust reverser

autopilot A
autopilot B

normal nose wheel steering
alternate nose wheel steering

landing gear
landing gear transfer unit.

power transfer unit (PTU)
autoslats

yaw damper

trailing edge flaps

(Boeing 737 NG FCOMv2 - 13.20.1 Hydraulics - System Description)


text:
Is QNET 2.0 VTOL Board Underactuated or Fully Actuated?
I'm working on a VTOL aircraft model, but the apparatus available in our lab is the QNET 2.0 VTOL Board.
The help I need is to confirm whether the VTOL Board is underactuated or fully actuated. As you guys have more knowledge and experience with practical systems, so I would greatly value your input. At first glance, it has one actuator, which is the propeller thrust, and one degree of freedom, which is the pitch angle. However, if we observe it in more detail, it also covers vertical displacement.
So, can we say that it is underactuated because it has two degrees of freedom and one degree of actuation? I have also attached a picture showing the equations of motion of the VTOL. Can you please share your insights by looking at this system? Any other thoughts or suggestions you think would be helpful would be greatly appreciated.
Thank you for your time and help.


text:
Airplane Owner, But don't have PPL. Can student pilot do oil change on their own plane?
Airplane Owner, But don't have PPL. Can student pilot do oil change on their own plane? I can't seem to find answer on this. Any helps would be great.

Great discussion and answer to the question on Reddit: https://www.reddit.com/r/flying/s/Ole3Ve2pO2

No. A student pilot cannot do preventive maintenace per 14 CFR § 43.3(g) and § 43.7(f):

Except for holders of a sport pilot certificate, the holder of a pilot certificate issued under part 61 may perform preventive maintenance

A person holding at least a private pilot certificate may approve an aircraft for return to service after performing preventive maintenance under the provisions of § 43.3(g).

I believe context makes it clear that "the holder of a pilot certificate" in the former part does not include student pilots. But in any case a student pilot cannot return the aircraft to service after preventive maintenance.
So, is an oil change preventive maintenance? 14 CFR Appendix-A-to-Part-43(c)(23) lists

Cleaning or replacing fuel and oil strainers or filter elements

as a preventive maintenance task. So a student pilot cannot clean or replace oil strainers or filter elements. As this is part of an oil change, it follows that a student pilot cannot do an oil change.
Note that a student pilot can add oil the same way they can add fuel- this isn't maintenance of any kind, just replenishing fluids. The Hochberg (2016) Interpretation mentions that this is not preventive maintenance, citing the fact that it does not appear in part 43 appendix A. If draining the oil is similarly simple, one could argue that that is not preventive maintenance either. So if by an "oil change" you just mean draining and refilling the oil that might be allowed. But replacing or cleaning filters or anything else involving disassembly is definitely not.

"I believe context makes it clear that "the holder of a pilot certificate" in the former part include student pilots." Is this sentence meant to say "doesn't"? Or is it ok for student to replace the oil, as long as someone else checks and returns it to service?

@jpa It means to say "doesn't," yes. Though maintenance can be done by anyone as long as they are supervised by an appropriately qualified individual so also yes a student (like anyone else) could change the oil (or overhaul an engine for that matter) if appropriately supervised.

Correct. A student pilot (or student mechanic) can perform the work as long as it's under the supervision of someone who is legally authorised to write off on said work. That's how student mechanics get experience, they do the work, a qualified mechanic inspects and certifies it (possibly after corrections).


text:
B777-300 secure cockpit door flaps
B777-300 secure cockpit door has two flaps for rapid decompression pressure going from cockpit to cabin.
What system is used internally to release the flaps? Subsidiary question: can the system be reactivated after decompression event or test, or is there any fusible part that needs to be changed?

This one is the sensor to trigger the opening of the door itself (from cabin to cockpit). For the other way, the air is going through those flaps I'm interested in.

This is not a direct answer for the 777. I don't know if Boeing is going to disclose the exact mechanism used today, for security reasons. Still they filed a patent shedding some light on how it could work.
From the patent:

Each panel is locked by an articulated hook (428 and 432)
The hook is locked by a pin (438) in a hole.
The pin is controlled by the pressure sensor (436).

When the pressure difference between door sides exceeds a threshold, the pin is recessed, releasing the hook, the panel can swing in both directions freely. The full process is fast enough to be compatible with an explosive decompression.
More:

Boeing patent.
Boeing 757/767 flight deck door.

In the second article it is said the panel can be closed/reset after the sensor has been triggered.
From what I read, there are single-plate panels and panels made of multiple small slats, protected by a grid to prevent any intrusion when the panel is open.


text:
Flying over the Grand Canyon SFAR - what altitude should you fly if you encounter clouds at appropriate altitude?
I was recently flying over the Grand Canyon on our way to St. George using the SFAR routes assigned.  We were flying with flight following and was assigned the appropriate altitude I had previously verified with the chart.  Shortly after entering the corridor, we encountered clouds.  I assumed since we had flight following, we were safe, but since I'm not instrument rated, I didn't feel it was appropriate VFR.  What altitude could we have flown at to be within the SFAR and/or should we have asked the controller for a different altitude?  The issue was that we were already 11,500 in a C-172, so climbing to 13,500 probably wasn't feasible.  Any suggestions?

I assumed since we had flight following, we were safe - NO. Flight following is NOT traffic separation. It is traffic advisories and safety alerts. You only get separation when you're in B/C/TRSA airspace, and even in C/TRSA you aren't separated from ALL traffic—only certain traffic.

I have flown that route and encountered this same situation. You have two options.
Climbing to 13,500

if your aircraft is capable
if you are confident of your physiological response to hypoxia at that level
if you are sure that you can descend back below 12.5 within 30 minutes (91.211) assuming that you are not oxygen equipped,
if your will have VFR appropriate cloud clearance 1000' above tops of clouds

Your other choice is a 180 course reversal to remain clear of clouds and exit the corridor.
As @randomhead points out, you could declare an emergency, but this would likely be received with some tough questions from the FSDO because this would appear to be an emergency of your own making where you clearly had a non-emergency "out" with a 180.

Having flight following in no way relieves you of your 91.155 cloud distance requirements. You are expected to comply with 91.155 at all times. If a published procedure or ATC instruction would cause you to violate 91.155 you are expected to speak up and request alternate instructions from ATC.
A VFR aircraft in IMC is an honest-to-goodness emergency, even if you were instrument rated which you aren't. As such you can invoke 91.3(b) PIC authority and do what you need to do in order to meet the emergency, that is, get out of the clouds.
You should have communicated what was happening to ATC and done something to get out of IMC—a climb, a descent, a 180º turn. Something.